1. Field of the Invention
The present invention relates to a workpiece picking device and a workpiece picking method for improving a picking operation of workpieces.
2. Description of the Related Art
Conventionally, for example, a device which picks items randomly piled in a storage, such as a container (workpieces randomly piled in a three-dimensional space) by a robot has been used in various fields. In such a workpiece picking device, for example, an operation stable until the last workpiece is picked is difficult in general.
For example, this is because while, to pick workpieces (items), an operation of approaching a hand of a robot to the workpieces (approach operation) is performed, an interference of the hand with the storage or other workpieces occurs and, as a result, a state in which the workpieces to be picked fail to be held occurs. Further, for example, when picking processing is performed while workpieces are held in a prescribed holding manner, a case in which such a prescribed holding manner fails to be realized with respect to the workpieces having a three-dimensionally optional posture also frequently occurs. Specifically, when only one manner of holding workpieces is prescribed, if a surface desired to be held faces downward, holding the workpieces in the prescribed holding manner becomes difficult.
Thus, in the workpiece picking device (random pile picking system), a case in which although workpieces remain in the storage, the workpieces may be no longer picked often occurs.
Incidentally, hitherto, for example, Japanese Laid-Open Patent Publication No. 2013-052490 discloses a workpiece picking device in which a failure of picking from a multitude of workpieces is reduced and a retry operation is also reduced, the workpiece picking device being designed to estimate ease of holding a part of workpieces measured by a sensor on the basis of information on success or failure in picking in the past stored in a database and not hold preferentially workpieces which seem to be difficult to be held, but adjust at least one of an opening/closing amount, an operation speed, and a holding force of a hand to perform a more careful picking operation when there are no other workpieces which seem to be capable of being held.
Further, hitherto, for example, Japanese Laid-Open Patent Publication No. 2016-132086 discloses a workpiece feeding technique for improving a probability of holding workpieces randomly piled and improving a success rate of an operation in a subsequent step, the workpiece feeding technique comparing measurement data in which workpieces randomly piled are measured with shape data of workpieces stored in advance to calculate a position and a posture of the workpieces, selecting workpieces to be held on the basis of the position of the workpieces as calculated, and associating a position and a posture of the workpieces as selected with a plurality of holding postures indicating a positional relationship between the workpieces and a holding mechanism as calculated in such a manner as to be capable of feeding the workpieces to a feeding target to determine a holding posture of the workpieces.
Further, hitherto, for example, Japanese Laid-Open Patent Publication No. 2012-183616 discloses a workpiece feeding technique for picking for reliably changing a position and a posture of workpieces randomly piled and generating a new random pile state in which a projection portion is provided in a manner movable forward and backward from a bottom portion to an upward inner side of a container body which is open upward in which a plurality of workpieces may be randomly piled, and the projection portion is operated in a manner movable forward and backward to pick the workpieces one by one by a robot hand mounted to a robot.
However, in the workpiece picking device as described above, for example, when a part of other workpieces is superposed on a workpiece to be picked, it is difficult to improve such a situation to pick the workpiece, and thus effects are limited. In addition, for example, to perform association with a plurality of holding postures, necessity to prepare candidates of a large number of holding postures arises, which is thus unrealistic. Further, for example, to operate the projection portion of the container body in a manner movable forward and backward, an exclusive hardware mechanism for allowing such an operation to be performed is to be provided, and if the workpieces are heavy items, there occurs also a case in which it is difficult to operate the projection portion in a manner movable forward and backward.
Thus, hitherto, various workpiece picking devices have been proposed, whereas there has been a problem that it is difficult to pick workpieces randomly piled in a satisfactory manner or an exclusive hardware mechanism is to be provided.
It is an object of the present invention is to aim to provide a workpiece picking device and a workpiece picking method which may reduce the number of workpieces difficult to be picked.